A stabilizer is a ball joint part connecting a suspension apparatus and a stabilizer apparatus. FIG. 1 is a perspective view showing a schematic structure of a front side wheel of a vehicle. Each suspension apparatus 10 is provided at left and right tires 30 and has an arm 11 and a cylinder 12. A lower end portion of the arm 11 is fixed at a bearing supporting a shaft of the tire 30. The cylinder 12 is elastically movable relatively to the arm 11. A bracket 13, to which a stabilizer link 200 is mounted, is provided at the arm 11. The suspension apparatus 10 supports the weight of a vehicle body that is applied to the tire 30. A stabilizer apparatus 20 is equipped with a bar 21 that is approximately U-shaped, and the stabilizer apparatus 20 is mounted to the vehicle body via bushes 22. The stabilizer apparatus 20 secures roll stiffness of the vehicle.
The stabilizer links 200 are provided at the bracket 13 of the suspension apparatus 10 and at the end portion of the bar 21 of the stabilizer apparatus 20. The stabilizer links 200 are connected to each other by a support bar 500. The stabilizer link 200 transmits a load, which is generated when the suspension apparatus 10 receives an input from a road surface, to the stabilizer apparatus 20.
FIG. 2 is a side sectional diagram showing a portion of a structure of a specific example of the stabilizer link 200. The stabilizer link 200 is equipped with a stud ball 201, a ball seat 301, a housing 302, and a dust cover 401. The stud ball 201 has a stud portion 210 and a ball portion 220 which are integrally formed.
The stud portion 210 has a tapered portion 211, a straight portion 212, and a screw portion 213. The tapered portion 211 is formed at an upper end portion of the ball portion 220. A collar portion 214 and a projection portion 215 are formed at an upper end portion and a lower end portion of the straight portion 212. A lip portion 411 of upper end portion of the dust cover 401 abuts between the collar portion 214 and the projection portion 215 at the straight portion 212 so as to be fixed therebetween. The screw portion 213 of the stabilizer link 200 proximate to the suspension apparatus 10 is fixed at the bracket 13 of the arm 11 by screw fastening, and the screw portion 213 of the stabilizer link 200 proximate to the stabilizer apparatus 20 is fixed at the bar 21 by screw fastening.
The ball seat 301 and the housing 302 form a pivot support member that universally supports the stud ball 201. The ball portion 220 of the stud ball 201 is press-fitted into the ball seat 301. Thermal caulking portions 323 are formed at a bottom portion of the ball seat 301. The housing 302 holds the ball seat 301 therein. Each thermal caulking portion 323 projects through a hole 302A of bottom portion of the housing 302, and the leading end portion of the thermal caulking portion 323 engages with a lower surface portion of the housing 302, so that the ball seat 301 is fixed at the housing 302. A fixing portion 412 of a lower end portion of the dust cover 400 is held between flange portions 321 and 311 of the ball seat 301 and the housing 302 (for example, Patent Documents 1 and 2).
Production for stabilizer link 200 is performed by the processes shown in FIG. 3. FIGS. 3A to 3E are side cross sectional views of portions of structures showing each process of a production method for the stabilizer link 200. In FIGS. 3A to 3E, the screw portion 213 is not shown. First, as shown in FIG. 3A, the lip portion 411 of the dust cover 401 is inserted and held between the collar portion 214 and the projection portion 215 so as to closely contact the straight portion 212 of the stud ball 201. Next, as shown in FIG. 3B, the ball portion 220 of the stud ball 201 is pressed into the ball seat 301. In this case, the fixing portion 412 of the dust cover 401 is disposed at the outer peripheral surface side (upper surface side in FIG. 3) of the flange portion 321 of the ball seat 301. Reference numeral 322 is a pin portion formed at a surface (surface which is opposite to a surface into which the ball portion 220 is pressed) of the ball seat 301.
Next, as shown in FIG. 3C, the housing 302 and the support bar 500, which are integrally formed, is mounted to the ball seat 301. In this case, the fixing portion 412 of the dust cover 401 is held between the flange portions 321 and 311 of the ball seat 301 and the housing 302, and the pin portions 322 project from the holes 302A of the housing 302 to the outside. Next, as shown in FIG. 3D, the pin portions 322 of the ball seat 301 are deformed by heating using a thermal caulking machine 350, so that the thermal caulking portions 323 are formed. Thus, the ball seat 301 is fixed at the housing 302, so that the stabilizer link 200 is obtained as shown in FIG. 3E.
In stabilizer links, in the conventional techniques, iron was used as a material for the housing and support bar. In recent years, in order to reduce the weights of stabilizer links, for example, aluminum is used as a material of the housing and support bar as proposed in, for example, Patent Documents 3 and 4, and resin is used as a material for the housing and support bar as proposed in, for example, Patent Document 5.
For example, in the techniques of Patent Documents 3 and 4, first, a ball seat made of resin is formed at a ball portion of a stud ball by injection molding. Thus, a subassembly having the ball portion and the ball seat is obtained. Next, the subassembly is inserted into a die as a core, melted aluminum alloy is injected into the die, and die casting is performed. A housing and a support bar, which are integrally formed, are obtained by this insert molding using the subassembly as a core. Next, after a stud portion is connected to the ball portion of the subassembly, a dust cover is mounted to the subassembly, so that a stabilizer link is obtained.
For example, in the technique of Patent Document 5, a housing and a support bar, which are made of resin, are integrally formed, and the housing and the support bar, which are integrally formed, are used for the production of the above stabilizer link 200. The housing and the support bar are used as the housing 302 and the support bar 500, which are integrally formed as shown in FIG. 3C, and the housing and the support bar are mounted to the ball seat 301. The process shown in FIG. 3D is performed, so that a stabilizer link is obtained.
Patent Document 1 is Japanese Unexamined Patent Application Publication No. Hei 6-117429, Patent Document 2 is Japanese Unexamined Patent Application Publication No. Hei 7-54835, Patent Document 3 is Japanese Unexamined Patent Application Publication No. 2004-316771, Patent Document 4 is Japanese Unexamined Patent Application Publication No. 2005-265134, and Patent Document 5 is Japanese Unexamined Patent Application Publication No. 2009-257507.